In radio controls for automobiles there is needed a control device which will turn the radio off with a simple push connection and then with a second pushing action turn the radio on again. This successive on-off by successive pushes is known in the art as a "push-push" switch actuation. The present invention is, of course, not limited to the operation of a radio in vehicles, but is especially useful in that type of device since the volume can be set so that immediately upon turning off and then turning on the radio again the same volume level will be maintained. There are other useful applications such as multipole, stepping, and selector switching all of which are contemplated for a so called push-push operating switch and the reference to a radio is only one convenient application.
In prior devices and particularly U.S. Pat. No. 3,204,067 "PUSH ROTARY SWITCH CONSTRUCTION WITH LOST MOTION CONTACT COUPLING" issued Aug. 31, 1965 to W. L. Brown and assigned to Boyne Products, Inc., there is illustrated a rotary switch of the push-push type in which successive pushing actions will successively produce on-off switch operation. However the switch action must be abrupt causing a crisp and definite engagement and disengagement of the switch members. If there is a lack of precision in the making and breaking of contacts in the switch operation, a slow disengagement time will produce excessive heating and wear of the switch members in addition to arcing and the like. In previously used push-push switches, the switch operation lacked a clean, quick on-off operation with the result that the lag occurring during the making and breaking of contacts and at other phases of actuation made the switch deficient in its definiteness of position and response that are so essential to applications such as radio on-off control.
Another impediment to the obtainment of a practical on-off, push-push switch in the prior art is the excessive number of components which greatly complicate the matter of assembly and construction of the switch. Obviously, a great number of components, all of which must be separately manufactured and assembled, adds considerably to the cost of producing the switch and maintaining it in good working order.
Another complication of the multiplication of components in the switch is the stack-up of tolerances which complicates the matter of proper assembly because each of the components varies in dimension and finish, and consequently the number of rejects and adjustments necessary to assemble such a multi-component system is directly proportional to the number of parts which are involved in its fabrication. In a push-push type switch, the central concept is that in one increment of operation switch actuation will occur, and then a second increment of operation will reset the switch for a successive operation. An unfortunate occurrence in prior art devices is an indefiniteness in the phase of plunger movement at which the switch actuation would occur, and the user would frequently, after having depressed the switch sufficiently to effect the on or off operation, have moved the plunger insufficiently so that upon retraction of movement the device is improperly reset to the same initial on-off position. This contributes to an unpopularity in the prior art devices of a push-push type switch. Accordingly, the accumulative drawbacks of the type of switch described has generally lead to a failing to adopt the particular switch in spite of obvious advantages inherent in that type of construction, not the least of which is that in radios a push-push type actuation rendered independently of volume control will ensure that once the radio is turned off and then re-actuated, it will resume the station at the same volume as occurred in the prior on position of the radio.